Powertrain control device

ABSTRACT

The object of this invention is to reduce shift shocks by controlling the driving torque during gear shift changing so that the driving torque is represented by a smooth, ideal waveform. 
     The driving torque calculating means estimates the output shaft torque of the automatic transmission from the engine torque characteristic or torque converter characteristic and, based on the estimated driving torque, generate a targeted torque pattern during gear shift changing. The engine torque control value calculating means calculates the control value for controlling the engine output torque, i.e., an ignition timing correction value Δθig, so as to eliminate the deviation between the targeted torque and the driving torque estimated by the driving torque calculating means. This ignition timing correction approximates the driving torque to the smooth targeted torque. This configuration realizes the object mentioned above.

This application is a continuation of application Ser. No. 08/548,470,filed Oct. 26, 1995, now U.S. Pat. No. 5,826,208.

FIELD OF THE INVENTION

The present invention relates to a method of controlling a vehicle withan automatic transmission and more particularly to an automotivepowertrain control device that reduces torque fluctuation generated atgear shift changing, so-called shift shock.

BACKGROUND OF THE INVENTION

Among conventional control methods of this kind are one described inJapanese Patent Publication No. 20817/1990, in which the starting andending points of an engine torque down control to reduce shift shocksare determined based on the engine rotation speed at the start of gearshift changing; one described in Japanese Patent Publication No.5688/1993, in which the starting and ending points of the engine torquedown control to reduce shift shocks are determined based on theinput/output rotation speed ratio, i.e., the ratio of the input shaftrotation speed (turbine rotation speed) and the output shaft rotationspeed (called a vehicle speed signal); and one described in JapanesePatent Publication No. 81658/1992, which determines the starting pointof the engine torque down control by the first method described aboveand the ending point of this control by the second method describedabove.

The engine torque down control of this kind of conventional control, asdescribed in Japanese Patent Publication No. 7213/1993, generallyswitches from a normal characteristic data memory of the engine controldevice to a gear shift changing characteristic data memory during theabove-mentioned period, and is required to search, through prestoredmaps, for the control timing and control value for every gear positionand engine load, and to control them.

FIG. 3 is a time chart that explains the shift shock reduction methodusing the above-mentioned conventional technique. This method uses anignition timing as the control value for engine torque down. Controltimings t1, t2 are determined to be the times when the input/outputrotation speed ratio exceeds prestored set values S1, S2. In thiscontrol period between t1 and t2, a prestored control value, i.e., anignition timing retard angle Δθ, is read out and added to a baseignition timing.

Hence, the corrected control value in this correction control period isconstant. When the output shaft torque in this control period is almostflat as shown, the retard control mentioned above can reduce torquefluctuation significantly. In other words, a so-called shift shockreduction effect is produced. The actual torque waveforms, however, varygreatly during that control period, making it impossible in many casesfor a constant correction value to produce a sufficient correctioneffect.

The set values S1, S2 and ignition timing retard angle Δθ need to bemade optimum by tuning at the development stage, requiring a very longtime. Even if they can be made optimum, change with time and change inenvironment may render the set values thus determined inadequate forcontrol, making it difficult to completely reducing the shift shocks.

SUMMARY OF THE INVENTION

The object of this invention is to provide a control device and method,which reduces the development man-hour by eliminating as many parts aspossible that require tuning and which can automatically follow upchange with time and change in environment to reduce shift shocks.

The object is achieved by a powertrain control device for vehicles whichincludes an automatic transmission having a torque converter; a controldevice incorporating at least one microcomputer and controlling theengine and the automatic transmission; a driving torque calculatingmeans for estimating the torque of the output shaft of the automatictransmission; a targeted torque generating means for producing atargeted torque based on the driving torque estimated by the drivingtorque calculating means, an engine torque control value calculatingmeans for calculating a control value for controlling the output torqueof the engine from the deviation between the targeted torque generatedby the target torque generating means and the driving torque estimatedby the driving torque calculating means; an engine torque control valuelimiting means in the engine torque control value calculating means, forlimiting the engine torque control value that exceeds a predeterminedvalue; and an engine torque control means for controlling the outputtorque of the engine in response to a signal from the engine torquecontrol value calculating means;

the automotive powertrain control device further comprising an estimateddriving torque monitoring means for monitoring the magnitude of theestimated driving torque determined by the driving torque calculatingmeans, and a line pressure control device for controlling the linepressure of the automatic transmission by the estimated driving torquemonitoring means.

Because the control device of this invention with the above-mentionedconfiguration feedback-controls the output shaft torque of the engine sothat the actual driving shaft torque approaches the targeted torque, andlearns the line pressure of the automatic transmission tofeedforward-control the line pressure according to the magnitude of theestimated driving shaft torque, an ideal torque control can be made atgear shift changing, significantly reducing the man-hour of thedevelopment by decreasing the number of parts which need tuning. Thedevice can also follow up automatically change with time and change inenvironment to appropriately reduce shift shocks.

To achieve the above objective, the powertrain control device of thisinvention comprises a targeted torque pattern generating means forproducing an ideal waveform of the driving shaft torque at gear shiftchanging, a driving torque calculating means for estimating the actualdriving shaft torque with high precision, an engine torque control valuecalculating means for calculating the control value for controlling theoutput torque of the engine so that the estimated driving torque followsup the targeted torque pattern, and an engine torque control means forcontrolling the output torque of the engine.

The targeted torque generating means can have a function of recognizingas an actual gear shift changing timing a time when an estimated turbinetorque determined by a turbine torque calculating means in the drivingtorque calculating means exceeds a predetermined value in a specifiedperiod of time after a gear shift change command, temporarily storingthe driving torque at the actual gear shift changing timing or anaverage driving torque up to that timing as a driving torque before thegear shift changing; calculating a driving torque after the gear shiftchanging from the ratio of the driving torque before the gear shiftchanging to the driving torque after gear shift changing; calculating aninclination angle with respect to the elapsed time of the targetedtorque from the difference between the driving torques before and afterthe gear shift changing and from a preset gear shift changing time; andcalculating the targeted torque according to the inclination angle everypredetermined cycle of calculation.

The engine torque control value calculating means can include adeviation calculating means for calculating a deviation between thetargeted torque value generated every predetermined cycle of calculationby the targeted torque generating means and the driving torque valuecalculated by the driving torque calculating means, and an engine torquecontrol value converting means for calculating an engine torque controlvalue by multiplying the deviation determined by the deviationcalculating means by a preset conversion coefficient. The conversioncoefficient is preferably set to zero when the driving torque value in afirst predetermined period after the actual gear shift changing timingis smaller than the targeted torque value, to a predeterminedcharacteristic value when the driving torque value is greater than thetargeted torque value in a second predetermined period, longer than thefirst period after the actual gear shift changing timing; and to a valueduring a period beyond the second predetermined period, which isdetermined by dividing the predetermined characteristic value by thecoefficient of the elapsed time.

The driving torque calculating means preferably includes a first drivingtorque calculating means for estimating the driving torque by using aprestored engine torque characteristic, a second driving torquecalculating means for estimating the driving torque by using a prestoredtorque converter characteristic, and a switching means for switching thecalculation by the second driving torque calculating means in a regionwhere the slip of the torque converter is small to the calculation bythe first driving torque calculating means in a region where the slip issmall in order to estimate the torque of the output shaft of theautomatic transmission. The load torque of accessory devices of theengine is preferably learned from the deviation between the drivingtorques generated by the first and second driving torque calculatingmeans and corrected when using the first driving torque calculatingmeans.

The first driving torque calculating means for estimating the drivingtorque by using the engine torque characteristic can include an enginetorque characteristic memory means for storing the engine torquecharacteristic beforehand, a means for calculating the slip ratio of thetorque converter, a means for calculating the torque ratio of the torqueconverter by receiving the slip ratio information from the slip ratiocalculating means, a turbine torque calculating means for outputting theoutput shaft torque of the torque converter determined by multiplyingthe engine torque read from the engine torque characteristic memorymeans by the torque ratio output from the torque ratio calculatingmeans, and an automatic transmission output shaft torque calculatingmeans for outputting the output shaft torque of the automatictransmission by multiplying the output shaft torque of the torqueconverter output from the turbine torque calculating means by the gearratio of the engaged gear position at present.

The engine torque characteristic memory means can store the enginetorque by taking as parameters the accelerator pedal opening or throttlevalue opening and the engine rotation speed, the intake air mass flowand engine rotation speed, the intake air pressure, intake airtemperature and engine rotation speed, or the pulse width for operatinga fuel injector and engine rotation speed.

The second driving torque calculating means for estimating the drivingtorque by using the characteristic of the torque converter can include amemory means for storing the characteristics of the input capacitycoefficient of the torque converter, a means for calculating the slipratio of the torque converter, a means for calculating the torque ratioof the torque converter by receiving the slip ratio information from theslip ratio calculating means, a torque converter input torquecalculating means for calculating the torque converter input torque bymultiplying the pump capacity coefficient read from the means forstoring the characteristics of the input capacity coefficient by anengine rotation speed squaring signal output from an engine rotationspeed squaring means, a turbine torque calculating means for outputtingthe output shaft torque of the torque converter determined bymultiplying the torque ratio output from the torque ratio calculatingmeans by the input torque of the torque converter from the torqueconverter input torque calculating means, and an automatic transmissionoutput shaft torque calculating means for calculating the output shafttorque of the automatic transmission by multiplying the output shafttorque of the torque converter output from the turbine torquecalculating means by the gear ratio of the engaged gear position atpresent.

According to this invention, the output shaft torque of the engine isfeedback-controlled so that the actual driving shaft torque is equal tothe targeted torque. This enables an ideal torque control at gear shiftchanging and hence a significant reduction in the man-hour required fortuning. This control also allows the device to follow up automaticallychange with time and change in environment, reducing shift shocks.

In calculating the engine torque control value by multiplying thedeviation between the targeted torque value and the estimated drivingtorque value by the conversion coefficient which is preset and storedbeforehand, the conversion coefficient is varied with time from theactual gear shift changing timing. This avoids the possibility ofover-correction and allows smooth connection of the driving torqueduring gear shift changing to the driving torque during the normalrunning after gear shift changing.

The driving torque calculating means comprises a first driving torquecalculating means that utilizes the engine torque characteristics and asecond driving torque calculating means that utilizes thecharacteristics of the torque converter. In a region where the slip ofthe torque converter is large, the second driving torque calculatingmeans is used and, in a region where the slip is small, the firstdriving torque calculating means is used, thereby enhancing theprecision of estimation of the driving torque.

Adoption of the driving torque estimation method for estimating thedriving torque through map search based on the measurement parameters,such as accelerator pedal opening, throttle valve opening, enginerotation speed, intake air mass flow, intake air pressure, intake airtemperature, pulse width for operating the fuel injector and torqueconverter slip ratio, allows the driving torque control that uses onlythe existing sensors incorporated for engine control without requiringexpensive torque sensors. This enhances the function without increasingthe cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the configuration of a system to which thisinvention is applied;

FIG. 2 is a block diagram showing an example of the configuration of acontrol device such as ATCU or ECU used in this invention;

FIG. 3 is a time chart showing an upshift shock and a conventionalmethod of reducing it;

FIG. 4 is a time chart showing a method of reducing upshift shock of afirst embodiment of this invention;

FIG. 5 is a graph showing a static line pressure characteristic used inthis invention;

FIG. 6 is a graph showing the characteristic of line pressure at gearshift changing;

FIG. 7 is a diagram showing a method of comparison of the upper andlower limits with torque and a judgment method of this invention;

FIG. 8 is a block diagram showing an example of a method for estimatingthe driving torque from the engine characteristic according to thisinvention;

FIG. 9 is a block diagram showing a method for estimating the drivingtorque from the torque converter characteristic according to thisinvention;

FIG. 10 is an error characteristic diagram of the method of estimatingthe driving torque based on the converter characteristic and enginecharacteristic according to this invention;

FIG. 11 is a block diagram showing the switching the driving torqueestimation method based on the torque converter characteristic and theengine characteristic according to this invention;

FIG. 12 is a time chart showing a method of reducing the upshift shockof a second embodiment of this invention;

FIG. 13 is a time chart showing a method of reducing the upshift shockof a third embodiment of this invention;

FIG. 14 is an example of a timer table;

FIG. 15 is a block diagram showing a first method of estimating thedriving torque from the engine characteristic;

FIG. 16 is a block diagram showing a second method of estimating thedriving torque from the engine characteristic;

FIG. 17 is a block diagram showing a third method of estimating thedriving torque from the engine characteristic;

FIG. 18 is a block diagram showing a fourth method of estimating thedriving torque from the engine characteristic;

FIG. 19 is a block diagram showing a method of estimating the drivingtorque from the torque converter characteristic;

FIG. 20 is an error characteristic diagram showing the method ofestimating the driving torque based on the torque convertercharacteristic and the engine characteristic;

FIG. 21 is a block diagram showing the switching the methods ofestimating the driving torque based on the torque convertercharacteristic and the engine characteristic; and

FIG. 22 is a detailed time chart showing a method of reducing theupshift shock of a fourth embodiment of this invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of this invention will be described in detail referring tothe accompanying drawings.

FIG. 1 is a view showing the configuration of a system to which thepresent invention is applied. Reference numeral 1 represents an engine,2 an automatic transmission (AT), 3 a propeller shaft, 4 a differentialgear that also serves as a final reduction gear, 5 drive wheels, and 6 ahydraulic control circuit. Designated 7 is a control unit (electroniccontrol device) for the AT incorporating a microcomputer, which isreferred to as an ATCU. Denoted 8 is a control unit (electronic controldevice) for engine incorporating a microcomputer, which is simplyreferred to as an ECU. Denoted 9 is an air cleaner, 10 an air flowsensor, 11 a throttle chamber, 12 an intake manifold, and 13 a fuelinjector for injecting fuel.

The AT 2 comprises a torque converter 14 and a gear train 15. It alsoincludes a turbine sensor 16 for detecting the output shaft rotationspeed of the torque converter 14, i.e., the input shaft rotation speedof the transmission, and a transmission output shaft rotation sensor 17for detecting the rotation speed of the transmission output shaft.

The ECU 8 receives information from a crank angle sensor 21, the airflow sensor 10 and a throttle sensor 18, and executes calculations ofsignals such as an engine rotation speed signal. The ECU 8 performs avariety of controls, which include a fuel control by outputting a valveopening drive signal to the injector 13, an assist air flow control byoutputting a valve opening drive signal to an idle speed control valveISC 19 and, though not shown, an ignition timing control by outputtingan ignition signal to an ignition spark plug. The ATCU 7 receivessignals from the transmission output shaft rotation sensor 17 and an ATfluid temperature sensor 22, and also receives the engine rotation speedand throttle valve opening signals from the ECU 8. Using these signals,the ATCU 7 performs calculations, and outputs a valve opening drivesignal for driving the open of a hydraulic control switch solenoid valve20 provided in a hydraulic control circuit, a drive signal for drivingthe ISC 19, and an ignition timing correction signal.

An example of the configuration of a control device such as the ATCU orECU mentioned above is shown in FIG. 2. The control device comprises atleast a CPU 33, a ROM 35, a RAM 36, an I/O interface circuit 38, and abus 34 interconnecting these. When the ATCU 7 and ECU 8 are connectedthrough a LAN, a LAN control circuit 37 is required, as shown in FIG. 1.

According to this invention, similar effects can be produced in thecontrol device of a type in which a single CPU having the functions ofthe ATCU and ECU by integrating them.

FIG. 4 is a time chart that explains a method of a first embodiment ofthis invention, of reducing the upshift shock. The gear shift changingcontrol is started by a shift changing command. The estimated turbinetorque is found at predetermined time intervals irrespective of the gearshift changing command. The method of estimating the turbine torque willbe described later. Though not shown, when a gear shift changing commandis issued, the hydraulic switch solenoid valve 20 for the gear positionis activated, engagement of the engagement friction elements such as aclutch and a brake for the gear position. Thus, the gear for the gearposition begins to be engaged. When the gear starts to be engaged, theestimated turbine torque increases almost stepwise as shown. This isbecause the upshift causes the engine rotation speed and the turbinerotation speed to fall quickly and the inertia components of the engineand so are added.

In this invention, the rising point of the estimated turbine torque isdetected and recognized with a slice level St, and the time t2 is usedfor a stepwise switch point of gear ratio, that is used for theestimated output shaft torque calculation, and for a generation point ofthe targeted torque pattern. Like the estimated turbine torque, theestimated output shaft torque is also calculated at predeterminedintervals irrespective of the shift command. The estimated output shafttorque is the output shaft torque of the transmission calculated bymultiplying the estimated turbine torque by the gear ratio at that time.When information on the time t2 is received, the gear ratio to be usedfor the above calculation is switched stepwise from the gear ratiobefore the gear shift changing command to the gear ratio after thecommand. This is because the rising point of the estimated turbinetorque is the starting point of switching from the gear before the shiftcommand to the gear after the shift command, and also a switch point ofthe torque transmission path.

This stepwise switching of the gear ratio causes the estimated outputshaft torque to decrease stepwise at time t2, after which it increasesin accordance with the waveform proportional to the rising waveform ofthe estimated turbine torque (see torque waveforms A, B, C shown).

When the gear engagement is completed, the estimated turbine torquereturns to the predetermined low value, as shown. The period duringwhich the estimated turbine torque is high on the upper base of atrapezoidal shape of the waveform is an actual gear engagement period,in which the engine rotation speed and the turbine rotation speed aresharply reduced. In this period, the inertia component of the torque isreleased and hence the estimated turbine torque is large on the upperbase of a trapezoidal shape. This period is called an inertia phase.Therefore, the estimated output shaft torque exhibits a waveformproportional to the estimated turbine torque waveform, allowing thetorque during the gear shift changing to be estimated with fidelity. Aperson on the vehicle senses the change with time of the estimatedoutput shaft torque and feels it as a shift shock. To reduce the shiftshocks, it is necessary to minimize the change with time of theestimated output shaft torque (torque fluctuation in the inertia phase).This invention accomplishes this requirement in the following manner. Attime t2, an average Tob of the estimated output shaft torque immediatelybefore the gear shift changing is calculated. The estimated output shafttorque is calculated at predetermined time intervals (10 ms, forexample) and stored successively in a RAM. In this case, an arbitrarynumber of estimated values (say, 14 values) are stored. When the latestestimated value is stored, the previously stored estimated values areshifted to the next memory locations, with the oldest value discarded.Hence, at time t2 all or a part of the stored estimated values are readout to calculate the average value Tob of the estimated output shafttorque immediately before the gear shift changing. Next, an output shafttorque Toa immediately after the gear shift changing is calculated usingthe formula Toa=(Tob/gear ratio before gear shift changing)×(gear ratioafter gear shift changing). From the difference between these torques,the output shaft torque difference ΔTo between the torques before andafter the gear shift changing is determined. A temporal inclinationangle θt of the targeted torque pattern during gear shift changing isdetermined from a preset targeted gear shift changing period Δtus andthe torque difference ΔTo. The targeted torque is calculated atpredetermined intervals by using the temporal inclination angle et fromthe time t0, as shown. As a result, the targeted torque pattern has aninclined characteristic during the gear shift changing, as shown. Inthis targeted torque pattern generation period, the deviation δ betweenthe estimated output shaft torque To calculated at predeterminedintervals and the target torque is determined. The engine ignitiontiming is corrected so that this deviation δ is rendered zero, in orderto control the engine output torque. The deviation δ is determined usingthe formula of (estimated output shaft torque To)-(targetedtorque)=deviation δ. When δ is positive, the firing timing is retarded;when δ is negative, the firing timing is advanced. In the example ofFIG. 4, however, when δ is negative during a predetermined period (forexample, 50 ms) from the time t2, the firing timing is not advanced, andwhen δ becomes positive, the firing timing is retarded. This is becausean attempt to correct the drop of the torque at the initial stage ofgear shift changing may increase the amount of advance of the ignitiontiming into the region where knocking occurs. If this influence can beignored, the above method of FIG. 4 need not be used.

The ignition timing correction value Δθig is calculated by multiplyingthe deviation δ by a specified conversion coefficient kc, i.e.,Δθig=kc×δ.

Next, a method of controlling the line pressure will be described. Thestatic line pressure PL0 before a shift command is issued is eitherformulated as a linear function of the estimated turbine torque Tt asshown in FIG. 5 and stored, or mapped and stored in memory. The PL0 isderived from an average of a specified number of estimated turbinetorques Tt, and the control is performed. It is ideal that the staticline pressure PL0 is determined and controlled in this way after theshift command until the time t2. Considering the waste time of hydraulicpressure acting on the clutch with respect to the step response of theline pressure control solenoid, the primary delay characteristic, theline pressure during gear shift changing is set to PL1 at time t1 apredetermined time t2 before this. The line pressure PL1 during gearshift changing is either formulated as a linear function of theestimated turbine torque Tt (Tt in a period t0-t1) as shown in FIG. 6and the function is stored in a memory or mapped or the map is stored ina memory. The PL1 is derived from an average of a specified number ofestimated turbine torques Tt and then controlled. When the function ofthe line pressure stored, a portion corresponding to the inclination ofFIG. 6 is stored as a constant in a RAM. The line pressure PL1 duringgear shift changing is generally set to a value a predetermined amountsmaller than the static line pressure PL0. Reducing the line pressurePL1 at gear shift changing results in a reduction in the output shafttorque in inertia phase. This is because the reduction in the hydraulicpressure applied to the clutch in the inertia phase prolong the clutchengagement time, causing the engine rotation speed to slowly change tothe lower speed side and thereby reducing the amount of the inertiacomponent torque released per unit time. Hence, as the line pressure PL1at gear shift changing is made smaller, the time Δtus required for gearshift changing becomes longer in proportion to that. Although in thetime chart of FIG. 4 the time of the inertia phase is constantregardless of the magnitude of the line pressure PL1 at gear shiftchanging, the actual time of inertia phase changes as mentioned above.For simplicity of explanation, in FIG. 4, the time is being constant.

Detailed explanations will be given to essential parts of thisinvention. In FIG. 4, the ignition timing correction value Δθig issubjected to retard limit at a predetermined value so that the ignitiontiming is not retarded any further. This is because retarding theignition timing until the estimated output shaft torque To comes intothe target torque pattern will cause the timing to enter a region wherethe combustion in engine is hindered very badly. From the middle of theinertia phase onward, therefore, the characteristic of the estimatedoutput shaft torque To gradually deviates from the target torquepattern. Hence, the estimated output shaft torque To during the inertiaphase may exhibit a variety of waveforms designated by A, B, C in FIG.4. Other possible factors responsible for different waveforms include 1)variation of generated torque among engines, 2) change with time of thegenerated engine torque, 3) variation of clutch engagement force withrespect to the AT hydraulic pressure, and 4) change with time of theclutch engagement force with respect to the AT hydraulic pressure. Thisinvention copes with these problems and makes improvements as follows.

In the period of Δt seconds from the time t2, i.e., a target torquepattern starting point, the estimated output shaft torque To is comparedwith an upper limit LV1 and a lower limit LV2 that are preset and storedbeforehand. When the estimated output shaft torque To is between theupper and lower limits LV1, LV2, as in the case of waveform A, the linepressure holds the current value till the next time. When the estimatedoutput shaft torque To is greater than the upper limit LV1, as in thecase of waveform B, a value B of the line pressure smaller than thecurrent value A by a given value is stored in a RAM to be read out nexttime. When the estimated output shaft torque To is smaller than thelower limit LV2, as in the case of waveform C, a value C of the linepressure larger than the current value A by a given value is stored in aRAM to be read out next time. With such a learning control introduced,it is possible to control and confine the estimated output shaft torqueTo during the inertia phase within a specified range at all timesirrespective of the above-mentioned machine variation and change withtime, thus maintaining the performance of gear shift changing at a highlevel.

There are a variety of methods for comparison of the estimated outputshaft torque To with the upper and lower limits LV1, LV2 and forjudgment thereof. One example of the methods will be explained belowreferring to FIG. 7. Let us consider two cases: one in which theestimated output shaft torque To exceeds the upper limit LV1intermittently, as shown by the waveform B'; and one in which theestimated output shaft torque To exceeds the lower limit LV2intermittently, as shown by the waveform C'. When To exceeds LV1 as inthe first case, the S1 counter starts adding up the excess amount.Although this counting operation continues until time t3, the integratedvalue or the S1 counter value is already saturated at time tc before t3.Hence, in the period between tc and t3, the counter value S1 is read andstored in a RAM. Then, comparison is made between the counter value S1and a first excess judgment value SL1, which is preset and storedbeforehand. When S1 is found greater than SL1, the following operation,as explained in FIG. 4, is performed. The line pressure PL1 at gearshift changing is reduced by a predetermined value ΔPL from the currentvalue

    PL1=PL1 (current value)-ΔPL

and stored in a RAM. The control of the next time is performed using thecorrected line pressure PL1 at gear shift changing.

When, on the other hand, To exceeds LV2 but not LV1, as in the lattercase, the counter integrated value S2 of the S2 counter is read outduring the period from tc to t3 and stored in a RAM. Then, the value S2is compared with a second excess judgment value SL2 that is preset andstored beforehand. When S2 is found greater than SL2, it is judged thatthe line pressure PL1 at gear shift change of current value is used thistime was appropriate and no correction is made. When S2 is found smallerthan SL2, the line pressure PL1 at gear shift changing is increased by apredetermined value ΔPL from the current value

    PL1=PL1 (current value)+ΔPL

and stored in a RAM. The control of the next time is performed using thecorrected line pressure PL1 at gear shift changing.

Next, a method of estimating the torque is explained. Torque estimationmethods are largely classified into two types: one that estimates thetorque from the engine characteristic and one that estimates the torquefrom the torque converter characteristic. Torque estimation based on theengine characteristic is realized by any of the following methods.

(1) A method of estimating the engine torque from the engine rotationspeed Ne and the throttle valve opening TV0.

(2) A method of estimating the engine torque from the engine rotationspeed Ne and the air mass flow Qa.

(3) A method of estimating the engine torque from the engine rotationspeed Ne and the intake air pressure and intake air temperature.

(4) A method of estimating the engine torque from the engine rotationspeed Ne and the injector pulse width.

The engine torque estimation method of (1) that estimates the torquefrom the engine rotation speed Ne and the throttle valve opening TV0will be described referring to FIG. 8. The engine torque Te is read fromthe map that is stored in a ROM beforehand. This map contains the enginetorque Te stored for every specified magnitude and correlated with Neand TV0. A block 40 receives the throttle valve opening TV0 from thethrottle valve opening sensor and the engine rotation speed Ne from thecrank angle sensor 21 (Ne may be supplied through ECU), searches throughthe map and performs interpolation calculation to determine the enginetorque Te at that time. A block 41 executes the computation of e=Nt/Ne,where Nt is the output rotation speed of the torque converter andcommonly called a turbine rotation speed, to determine the slip ratio eof the torque converter. The turbine rotation speed may be determinedeither by directly detecting it by means of the turbine rotation speedsensor 16 or by indirectly determining it by dividing the vehicle speedVsp by the gear ratio at that time. A block 42 searches through thecharacteristic map of the torque ratio t in connection with e andperforms interpolation calculation to find the corresponding torqueratio t of the torque converter (=(torque converter output torqueTt)/(torque converter input torque Te)). A block 43 calculates theformula of Tt=Text to determine the output torque Tt of the torqueconverter, i.e., the turbine torque Tt. A block 44 multiplies theturbine torque Tt by the gear ratio at that time to determine the outputshaft torque To of the transmission.

Next, a method of estimating the torque from the torque convertercharacteristic will be explained referring to FIG. 9. A block 41receives the engine rotation speed Ne from the crank angle sensor 21 (Nemay be supplied through the ECU) and performs calculation of e=Nt/Ne,where Nt is the output rotation speed of the torque converter andcommonly called a turbine rotation speed, to determine the slip ratio eof the torque converter. This turbine rotation speed may be determinedeither by directly detecting it by means of the turbine rotation speedsensor or by indirectly determining it by dividing the vehicle speed Vspby the gear ratio at that time. A block 47 takes in the slip ratio e,searches through the characteristic map, stored in a ROM beforehand, ofthe slip ratio e and the torque converter input capacity coefficient Cpand performs interpolation calculation to find the Cp value at thattime. A block 48 calculates Ne2 and a block 49 performs calculation ofTp=Cp×Ne2 to determine the input torque Tp (=Te) of the torqueconverter. The subsequent routine is the same as that shown in FIG. 8and its explanation will be omitted.

As described above, the method of estimating the output shaft torque,i.e., the driving torque, of the transmission is largely classified intothe one that uses the engine characteristic and the one that uses thetorque converter characteristic. It Is desirable from the standpoint ofestimation accuracy that the two methods be selectively used inappropriate regions. FIG. 10 shows an example of the characteristic. Inthe method that uses the torque converter characteristic, as the slipratio e increases, the input capacity coefficient Cp rapidly approacheszero, in other words, the inclination of Cp with respect to e becomessharp, increasing the estimation error. On the other hand, the methodusing the engine characteristic is a method for estimating the outputtorque of the engine, and cannot estimate the load torque components ofaccessory devices, such as air conditioner, power steering oil pump andhead lamps. This second method therefore involves an estimation errorcorresponding to the load torque component of the accessory devices. Inregion where the load torque of the accessory devices is relativelylarge compared with the output torque of the engine, i.e., in thelow-speed and light-load operation region, the estimation error islarge. Hence, the two methods are selectively used according to themagnitude of the slip ratio e. That is, when e≦A where A is boundaryvalue of the slip ratio e between the two regions, the method using thetorque converter characteristic is used; and when e>A, the method usingthe engine characteristic is adopted.

FIG. 11 is a block diagram showing the method of learning theabove-mentioned load torque component of accessory devices. A block 50calculates the output torque Te of the engine by the method using theengine characteristic, and a block 51 calculates the input torque Tp ofthe torque converter by the method using the torque convertercharacteristic. A block 53 is a selector for selecting a method from thetwo methods according to the magnitude of the slip ratio e. A block 52,when e≦A, executes calculation of Tacc=Tp-Te at all times to determinethe load torque Tacc of accessory devices , stores in a RAM the averageof a specified number of calculated load torques, and updates the storedaverage for every predetermined number of calculations. When e>A and themethod using the engine characteristic for calculating the engine outputtorque Te is selectively used, the latest accessory devices load torqueTacc learned and stored in the block 52 is added to the engine outputtorque Te to calculate the torque converter input torque Tp and to useit for the driving torque estimation.

FIG. 12 is a time chart showing the method of reducing shocks atup-shift, of a second embodiment of this invention. This shock reducingmethod is similar to the one of FIG. 4, except that the temporaryinclination angle θt of the targeted torque pattern differs from theangle of FIG. 4. In such a way, the value θt can be adequatelydetermined. Because this method is basically similar to FIG. 4, detailedexplanation will be omitted.

FIG. 13 shows a third embodiment of this invention. This is a time chartshowing the method of reducing shocks at up-shift, as in the case ofFIG. 4. Only the points that differ from those of FIG. 4 will beexplained below.

The ignition timing correction value Δθig is calculated by multiplyingthe deviation δ thus determined by a specified conversion coefficientkc,

    Δθig×kcΔδ

This calculation is performed in the time range between t0 and t2. Inthe time range between t2 and t3, the ignition timing correction valueΔθig is calculated as follows to smoothly end the torque feedbackcontrol performed in the above-mentioned way.

    Δθig=(kc/N)×δ

where N is the number of times that the ignition timing correction valueΔθig is calculated at a predetermined calculation cycle after time t2 ora monotonously increasing function of time, and N takes a value of 1 orlarger. The conversion coefficient kc or kc/N is a sort of feedbackcontrol gain, which is constant during the period between t0 and t2 andis decreased with time during the period between t2 and t3. The time t2is the timing at which to change the control gain, and the time t3 isthe timing at which to stop the ignition control and to restore the linepressure.

Next, a method of controlling the line pressure will be described. Forthe static line pressure before a shift command, a first line pressurePL1 is during gear shift changing is determined from the estimatedturbine torque immediately after the shift command; at time t1, a secondline pressure PL2 during gear shifting is determined so that it issmaller than the first line pressure PL1 by a specified ratio; and attime t3, the line pressure is returned to the static line pressure PL0'after gear shifting. If there is a possibility that, if the linepressure is set to the first line pressure PL1 during gear shiftchanging immediately after the shift command, the gear engagement starttiming (t0 shown in the figure may be delayed), it is possible to usethe static line pressure PL0 up to time t0 or slightly before it, andthereafter set the line pressure to the first line pressure PL1 at gearshift changing.

By performing the above-mentioned control, the estimated output shafttorque To is expressed by a waveform that almost follows up the targettorque pattern, as indicated by a dashed line in FIG. 13, greatlyreducing the shift shock.

The timer values Δtus, t1, t2, t3 used in FIG. 13 are stored in a tableas control constants for each kind of gear shift changing, as shown inFIG. 14, and read out as required. There is no need to use all the timervalues shown above. For example, t1 and t2 may not be used. Instead,variables such as the ratio between the input rotation speed (called aturbine rotation speed) and the output rotation speed (vehicle speedsignal) of the transmission, i.e., the input/output rotation speedratio, or the ratio between the engine rotation speed and (vehiclespeed×gear ratio after gear shift changing), i.e., the pseudo torqueconverter slip ratio may be used, and the operation that is performed att1 and t2 may be executed when this ratio reaches a specified value. Theuse of the above rotation information often allows the control timing tobe determined more precisely.

The method of torque estimation will be detailed below. This method maybe classified largely into a method that estimates the torque from theengine characteristic and a method that estimates it from the torqueconverter characteristic. The torque estimation based on the enginecharacteristic may be realized by any of the following methods.

(1) A method of estimating the engine torque from the engine rotationspeed Ne and the throttle valve opening TV0.

(2) A method of estimating the engine torque from the engine rotationspeed Ne and the air mass flow Qa.

(3) A method of estimating the engine torque from the engine rotationspeed Ne and the intake air pressure and intake air temperature.

(4) A method of estimating the engine torque from the engine rotationspeed Ne and the injector pulse width.

FIG. 15 is a control block diagram showing how the engine torque isestimated from the engine rotation speed Ne and the throttle valveopening valve TV0. The engine torque Te is read from the map that isstored in a ROM beforehand. This map contains the engine torque Testored for every specified magnitude and correlated with Ne and TV0. Ablock 40 receives the throttle valve opening TV0 from the throttle valveopening sensor and the engine rotation speed Ne from the crank anglesensor (Ne may be supplied through ECU), searches through the map andperforms interpolation calculation to determine the engine torque Te atthat time. A block 41 executes the computation of e=Nt/Ne, where Nt isthe output rotation speed of the torque converter and commonly called aturbine rotation speed, to determine the slip ratio e of the torqueconverter. The turbine rotation speed may be determined either bydirectly detecting it from the turbine rotation speed sensor or byindirectly determining it by multiplying the vehicle speed Vsp by thegear ratio at that time. The block 42 searches through thecharacteristic map of the torque ratio t corresponding to e and performsinterpolation calculation to find the torque ratio t of the torqueconverter (=(torque converter output torque Tt)/(torque converter inputtorque Te)). A block 43, using the formula of Tt=Text, determines theoutput torque Tt of the torque converter, i.e., turbine torque Tt. Ablock 44 multiplies the turbine torque Tt by the gear ratio at that timeto determine the output shaft torque To of the transmission.

FIG. 16 is a control block diagram showing how the engine torque isestimated from the engine rotation speed Ne and the air mass flow Qa.What differs from the method shown in FIG. 15 is that the air mass flowQa is used instead of TV0. By the method of FIG. 15, estimation of theengine torque with high precision is difficult in environments in whichthe density of ambient air changes excessively, as at high altitudes andhigh and low temperatures. When high precision control is considered tobe essential in such environments, the method of FIG. 16 is desirable.

FIG. 17 is a control block diagram showing the method of estimating theengine torque from the engine rotation speed Ne and the intake airpressure and temperature. What differs from the method of FIG. 16 isthat the intake air pressure and temperature are used as sensorinformation instead of the air mass flow Qa. The sensor information issupplied to the block 45 to calculate the air mass flow Qa. In the caseof a four-cycle four-cylinder engine, the block 45 determines the airmass flow Qa according to the following formula.

    Qa=[(Ne/60)Vc·η·Pa]/(2·R·Ta)

where R is the gas constant, Ta is the intake air temperature, Pa is theintake air pressure, Vc is the engine displacement, and η is thecharging efficiency. This method is expected to produce the similareffects to those of the method shown in FIG. 16.

Alternatively, the intake air pressure Pa may be used instead of the airmass flow Qa and the engine torque map may be searched by using theintake air pressure Pa and the engine rotation speed Ne. In this case,the block 45 is omitted; a map is prepared which contains Te stored forevery predetermined magnitude and correlated with Ne and Pa; the map issearched by using the intake air pressure Pa detected by the sensor andthe engine rotation speed Ne, and interpolation calculation is performedto determine the engine torque Te; and then the output shaft torque Toof the transmission is determined in a similar way to the one describedabove.

FIG. 18 is a control block diagram showing the method of estimating theengine torque from the engine rotation speed Ne and the injector pulsewidth Ti. What differs from the method shown in FIG. 15 is that theinjector pulse width Ti is used instead of TV0. A block 46 determinesthe injector pulse width Ti from the engine state information such as Neand Qa (a part of the engine control routine) and calculates Te from Tiand Ne. A block 46 calculates Ti according to the following formula.

    Ti=Qa·K/Ne+Ts

where K is a constant and Ts is the injector response delay. The firstterm of the above formula calculated from Qa and Te corresponds to theeffective pulse width.

The advantage of this method is that the engine torque can be estimatedwith high fidelity even when the ratio A/F of air-fuel mixture suppliedto the engine changes depending on the parameters such as cooling watertemperature and throttle valve opening in addition to Qa and Ne. Thismethod is particularly useful even at times of low-temperature startwarm-up, sharp acceleration output mixture, and switching between leanburn and rich burn. Ti may also be a value from ECU.

Next, the method of estimating the torque from the torque convertercharacteristic will be described referring to FIG. 19. A block 41receives Ne from the crank angle sensor (Ne may be supplied through ECU)and performs calculation of e=Nt/Ne, where Nt is the output rotationspeed of the torque converter and commonly called a turbine rotationspeed, to determine the slip ratio e of the torque converter. Theturbine rotation speed may be determined either by directly detecting itfrom the turbine rotation speed sensor or by indirectly determining itby multiplying the vehicle speed Vsp by the gear ratio at that time. Ablock 47 takes in the slip ratio e, searches through the characteristicmap, stored in ROM beforehand, of the slip ratio e and the torqueconverter pump capacity coefficient Cp and performs interpolationcalculation to find the Cp value at that time. A block 48 calculates Ne²and a block 49 performs calculation of Tp=Cp×Ne² to determine the inputtorque Tp (=Te) of the torque converter. The subsequent routine is thesame as those shown in FIGS. 15 to 18 and its explanation will beomitted.

As mentioned above, the method of estimating the output shaft torque ofthe transmission, i.e., the driving torque is classified largely intothe method using the engine characteristic and the method using thetorque converter characteristics. It is desirable from the standpoint ofestimation precision that these methods be selectively used according tothe operation region. FIG. 20 shows an example of the characteristic. Inthe method that uses the torque converter characteristic, as the slipratio e increases, the input capacity coefficient Cp rapidly approacheszero, in other words, the inclination of Cp with respect to e becomessharp, increasing the estimation error. On the other hand, the methodusing the engine characteristic is a method for estimating the outputtorque of the engine, and cannot estimate the load torque component ofaccessory devices, such as air conditioner, power steering oil pump andhead lamps. This second method therefore produces an estimation errorcorresponding to the load torque components of the accessory devices. Inthe region where the load torque of the accessory devices is relativelylarge compared with the output torque of the engine, i.e., in thelow-speed and light-load operation region, the estimation error islarge. Therefore, the two methods are selectively used according to themagnitude of the slip ratio e. That is, when e≦A where A is the boundaryvalue of the slip ratio between the two regions, the method using thetorque converter characteristic is used; and when e>A, the method usingthe engine characteristic-based method is adopted.

FIG. 21 is a block diagram showing the method of learning theabove-mentioned load torque components of accessory devices. A block 50calculates the output torque Te of the engine by the method using theengine characteristic, and A block 51 calculates the input torque Tp ofthe torque converter by the method using the torque convertercharacteristic. A block 53 is a selector for selecting a suitable methodfrom the two method according to the magnitude of the slip ratio e. Ablock 52, when e≦A, executes calculation of Tacc=Tp-Te at all times todetermine the load torque Tacc of the accessory devices, stores in a RAMthe average of a specified number of the calculated load torques, andupdates the stored average for every predetermined times ofcalculations. When, for example, e>A and the selector selects the methodusing the engine characteristic to calculate the engine output torqueTe, the latest accessory devices load torque Tacc learned by the block52 and stored is subtracted from the engine output torque Te tocalculate the torque converter input torque Tp for the driving torqueestimation.

FIG. 22 is a detailed time chart showing the torque feedback control, ofa fourth embodiment of this invention. This shows the control betweentimes t0 and t3 in FIG. 13 in detail. In the following explanation, itis assumed that the estimated torque changes as shown in FIG. 22, incontrast to the target torque pattern generated at a certain inclinationfrom time t0. Actually, the targeted torque value tTon and the enginetorque value Ton are calculated in each calculation cycle Δts and usedfor the torque feedback control.

During the period in which the targeted torque pattern is generated, thedeviation δ between the estimated output shaft torque Ton calculated atpredetermined time intervals Δts and the targeted torque tTon isdetermined. The ignition timing is corrected in such a way as to makethe deviation δ zero, thereby controlling the output torque of theengine. The deviation δ is determined as follows.

    (estimated output shaft torque Ton)-(targeted torque tTon)=deviation .delta.

When δ is positive, the ignition timing is retarded and, when it isnegative, the timing is advanced.

In the example of FIG. 22, however, when δ is negative during apredetermined period ΔTx (for example, 50 ms) from the time t0, theignition timing is not advanced; and when δ become positive, theignition timing is retarded. This is because an attempt to correct thedrop of the torque at the initial stage of gear shift changing mayincrease the amount of advance of the ignition timing to the regionwhere knocking occurs. When this influence can be ignored, the abovemethod need not be used.

The ignition timing correction value Δθig is calculated by multiplyingthe deviation δ by the predetermined conversion coefficient kc, i.e.,

    Δθig=kc×δ

This calculation is performed in the time range between t0 and t2. Inthe time range between t2 and t3, the ignition timing correction valueΔθig is calculated as follows to smoothly end the torque feedbackcontrol performed in such a way.

    Δθig=(kc/N)×δ

where N is the number of times that the ignition timing correction valueΔθig is calculated at a predetermined calculation cycle after time t2 ora monotonously increasing function of time, and N takes a value of 1 orlarger. The conversion coefficient kc or kc/N is a sort of feedbackcontrol gain, which is constant during the period between t0 and t2 andis decreased with time during the period between t2 and t3.

At time t0+Δts, 67₁ =To₁ -tTo₁ <0. Because it is in the range of ΔTx,the conversion coefficient kc is taken to be zero, and the value 0 issubstituted into Δθig₁ =kc×δ₁ results in Δθig₁ =0. Hence, the ignitiontiming correction value 0 is output. Next, at time t0+2Δts, a similarcalculation is performed and the ignition timing correction value 0 isoutput. Next, at time t0+3Δts, 67₃ =To₃ -tTo₃ >0. The conversioncoefficient kc is set to a predetermined value B and Δθig₃ =kc×δ₃ isoutput as the ignition timing correction value (retard). At timet0+4Δts, too, a similar calculation is performed. Until time t2, thisroutine is repeated to output the ignition timing correction value(retard).

At time t2, formula Δθig=(kc/N)×δ is used to calculate the ignitiontiming correction value. First, at time t2+Δts, N=1 is substituted intothe formula and Δθig=(kc/1)×δ is calculated. At time t2+2Δts, N=2 issubstituted into the formula and Δθig is calculated. At time t2+3Δts,N=3 is substituted into the formula and Δθig is calculated. Thisprocedure is repeated and each Δθig is outputted. At time t2,δ=To-tTo<0. Because t2 is outside the range of ΔTx, the formulaΔθig=(kc/N)×δ is used as it is to output the ignition timing correctionvalue Δθig. From this point forward, the ignition timing correctionvalue is an advance. When the end point of target torque pattern tf isreached, the torque feedback control (ignition timing correctioncontrol) is ended.

According to this invention, the torque during gear shift changing isfeedback-controlled to follow up the targeted torque, which is so set asto ensure smooth change from a gear position to the subsequent gearposition. This eliminates the need to map and store in a ROM the enginetorque control start and end timings and the engine torque control value(for example, ignition timing correction value), both of which haveconventionally been tuned for each throttle valve opening and gearposition. The tuning man-hour is significantly reduced, and hence thedevelopment time can be shortened. Because the targeted torque, which isset to ensure smooth transition from one gear position to another, isfollowed, the shift shocks can be greatly reduced. Furthermore, evenwhen the engine changes with time or when the engine torquecharacteristic greatly deviates from the standard one while driving in ahighland or in a very cold or hot district, a targeted torque isgenerated from the engine torque in such a situation, the engine torqueis feedback-controlled, ensuring stable and smooth gear shift changing.

What is claimed is:
 1. A powertrain control device for a vehicle havingan engine, an automatic transmission, a torque converter, a transmissionchange signal generator for generating a transmission change signal at atransmission change timing, and a line pressure control device forcontrolling a line pressure of the automatic transmission, comprising:atleast one microcomputer to control the engine and the automatictransmission, wherein the powertrain control device has functions asfollows:(a) calculating a present output shaft torque of the automatictransmission; (b) calculating a target torque based on the calculatedpresent output shaft torque at a predetermined time after generating thetransmission change signal; (c) calculating an ignition timingcorrecting value by using a specified conversion coefficient and adeviation between the calculated present output shaft torque and thecalculated target torque; (d) outputting an engine control signal forcontrolling the engine based on the calculated ignition timingcorrecting value.
 2. A powertrain control device for a vehicle having anengine, an automatic transmission, a torque converter, a transmissionchange signal generator for generating a transmission change signal at atransmission change timing, and a line pressure control device forcontrolling a line pressure of the automatic transmission, comprising:atleast one microcomputer to control the engine and the automatictransmission, wherein the powertrain control device has functions asfollows:(a) calculating a turbine torque of the automatic transmissionat predetermined time intervals irrespective of the transmission changesignal; (b) calculating a first line pressure value at a predeterminedtime interval of the transmission change signal for controlling the linepressure approaching the first line pressure value based on thecalculated turbine torque; (c) outputting a first line pressure controlsignal to the line pressure control device; (d) calculating a secondline pressure value at a predetermined time interval of the transmissionchange signal for controlling the line pressure approaching the secondline pressure value based on the calculated turbine torque; (e)outputting a second line pressure control signal to the line pressurecontrol device; (f) outputting a third line pressure control signal forcontrolling the line pressure being returned to the static line pressureafter the transmission change timing to the line pressure controldevice.